As shown in FIG. 14, a solar power generation system has solar cell panels (solar cell modules M) installed on a house roof to supply electric power from the modules M through a connection box Q, an inverter R and a distribution board S to electrical apparatuses E. The solar cell modules are arranged so as to be flush with one another and are connected in series or parallel through terminal boxes B. Each terminal box B is fixed by adhesion to the back of the module M with watertightness kept using seal material.
As shown in FIG. 15, a conventional terminal box B has a pair of terminal boards 2 arranged side by side in a top-open box body 1. Positive and negative electrodes a of a solar cell module M are connected to the respective terminal boards 2. A diode 3 for preventing countercurrent is mounted between the terminal boards 2 and cables P for outside connection are connected to the terminal boards 2 (see Patent publication 1). In FIG. 15, numeral 6 denotes a cover.    Patent publication 1: JP patent publication 11-26035A
Another terminal box B is known which is provided with three or more terminal boards 2 to connect a plurality of solar cell modules M for improved performance of the solar cell modules and higher current collecting efficiency (see Patent publication 2). In this terminal box B, too, a diode 3 for preventing countercurrent is provided between each adjacent pair of the terminal boards 2.    Patent publication 2: JP patent publication 2002-359389A